Apparatus and method for accessing the bone marrow

ABSTRACT

An apparatus and method for accessing the bone marrow of a human&#39;s sternum is provided. The apparatus includes a tissue penetrator configured to penetrate the sternum, a trigger mechanism configured to engage when the tissue penetrator contacts the sternum and a depth control mechanism operable to limit the penetration of the tissue penetrator into the sternum to a pre-selected depth.

RELATED APPLICATION

This application claims priority to U.S. Provisional Patent Application Ser. No. 60/519,462, filed Nov. 12, 2003, and entitled “Apparatus and Method for Accessing the Bone Marrow of the Sternum.” This application also claims foreign priority to Taiwan Patent Application Serial No. ______, filed Nov. 11, 2004, and entitled “Apparatus and Method for Accessing the Bone Marrow of the Sternum.” This application is a continuation of U.S. application Ser. No. 10/987,051 filed Nov. 12, 2004 and entitled “Apparatus and Method for Accessing the Bone Marrow of the Sternum.”

TECHNICAL FIELD

The present invention is related in general to an apparatus and method to access the bone marrow and specifically to an apparatus and method for accessing the bone marrow of a human's sternum.

BACKGROUND OF THE INVENTION

Every year, millions of patients are treated for life-threatening emergencies in the United States. Such emergencies include shock, trauma, cardiac arrest, drug overdoses, diabetic ketoacidosis, arrhythmias, burns, and status epilepticus just to name a few. For example, according to the American Heart Association, more than 1,500,000 patients suffer from heart attacks (myocardial infarctions) every year, with over 500,000 of them dying from its devastating complications. In addition, many wounded soldiers die unnecessarily because intravenous (IV) access cannot be achieved in a timely manner. Many soldiers die within an hour of injury, usually from severe bleeding and/or shock.

An essential element for treating all such emergencies is the rapid establishment of an IV line in order to administer drugs and fluids directly into the circulatory system. Whether in the ambulance by paramedics, in the emergency room by emergency specialists or on the battlefield by an Army medic, the goal is the same—to start an IV in order to administer life-saving drugs and fluids. To a large degree, the ability to successfully treat such critical emergencies is dependent on the skill and luck of the operator in accomplishing vascular access. While it is relatively easy to start an IV on some patients, doctors, nurses and paramedics often experience great difficulty establishing IV access in approximately 20 percent of patients. The success rate on the battlefield is much lower where Army medics are only about 29 percent successful in starting an IV line during emergency conditions in the field. These patients are probed repeatedly with sharp needles in an attempt to solve this problem and may require an invasive procedure to finally establish an intravenous route.

In the case of patients with chronic disease or the elderly, the availability of easily-accessible veins may be depleted. Other patients may have no available IV sites due to anatomical scarcity of peripheral veins, obesity, extreme dehydration or previous IV drug use. For these patients, finding a suitable site for administering lifesaving drugs becomes a monumental and frustrating task. While morbidity and mortality statistics are not generally available, it is known that many patients with life-threatening emergencies have died of ensuing complications because access to the vascular system with life-saving IV therapy was delayed or simply not possible. For such patients, an alternative approach is required.

The intraosseous (IO) space provides a direct conduit to the systemic circulation and, therefore, is an attractive alternate route to administer IV drugs and fluids. Intraosseous infusion has long been the standard of care in pediatric emergencies when rapid IV access is not possible. The military used hand-driven IO needles for infusions extensively and successfully during World War II, but the needles were cumbersome, difficult to use, and often had to be driven into the bone. Drugs administered intraosseously enter the circulation as rapidly as they do when given intravenously. In essence, the bone marrow is considered to be a large non-collapsible vein.

Although effective in achieving IO access, the currently available IO infusion devices suffer from several significant limitations. Current devices are single-use only and bulky, which limits the number of devices a medic can take into the field. Manually inserted IO needles are very difficult to use in hard adult bones. Current devices frequently penetrate not only the anterior bone cortex, but may also the posterior cortex. In addition, some current devices pose a significant risk of shattering the bone upon use. After the needle is inserted, many current devices suffer from a high rate of dislodgement from the bone because of the non-axial manner in which they must be inserted. Dislodgement often leads to extravasation (leakage of fluid from the entry points of the needle).

SUMMARY OF THE INVENTION

In accordance with teachings of the present invention, various embodiments of an apparatus to access the bone marrow of a human's sternum are provided including various embodiments of a means to control depth of penetration into the bone marrow. In some embodiments, an apparatus of the invention includes a tissue penetrator configured to penetrate the sternum, a power mechanism operable to drive the tissue penetrator into the sternum (driver), and a depth control mechanism operable to control the depth of penetration of the tissue penetrator into the sternum. The tissue penetrator may include a pressure-sensitive probe capable of transmitting pressure changes to a sensor within the apparatus. The power mechanism may include axial force delivered by an operator. A driver may include a power source selected from the group consisting of a motor, a battery, a coiled spring, compressed gas, and a solar power cell. A tissue penetrator may include an outer cannula and an inner trocar. A tissue penetrator assembly may include a tissue penetrator, a connector such as a luer lock, a collar, and/or a blade. A depth control mechanism may include a trigger, physical stops at preset positions, a revolutions-per-minute (RPM) sensor, a torque sensor, a power sensor, a reverse clutch, a gear, an ultrasound sensor, and/or a depth probe or sensor. A trigger may be operably connected to the motor and/or a switch such that upon meeting a preset condition (e.g. change in RPM or torque, change in power consumption, physical contact with bone), tissue penetrator advancement is either terminated or proceeds to a preset depth level.

According to some embodiments of the invention, the driving force for tissue penetration is derived in whole or in part from the application of pressure by the operator. The applied pressure may activate a driver according to the invention. When the applied pressure surpasses a preset threshold, it may engage a manual driver means whereby operator action (e.g. pressure or movement) directly advances the tissue penetrator.

The present invention also provides a tissue penetrator that includes a means, whereby the tissue penetrator itself serves as the depth probe. Thus, the tissue penetrator itself may include a sensor operably linked to a trigger that, in turn, is operably linked to the driver.

In addition, the present invention provides a method of rapidly establishing access to intraosseous circulation via the intraosseous space including contacting a subject with an apparatus having a tissue penetrator configured to penetrate the sternum, a driver operable to drive the tissue penetrator into the sternum, and a depth control mechanism operable to control the depth of penetration of the tissue penetrator into the sternum and deploying the tissue penetrator.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete and thorough understanding of the present embodiments and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings, in which like reference numbers indicate like features, and wherein:

FIG. 1 is a schematic drawing showing the gross bone structure of the sternocostal region of a human;

FIG. 2A is a schematic drawing showing a longitudinal cross-section of an apparatus for accessing sternal bone marrow and a human sternum, wherein the apparatus is positioned on the skin of a human at the location shown in FIG. 1 and the tissue penetrator has penetrated the skin and muscle;

FIG. 2B is a schematic drawing of the apparatus and sternum shown in FIG. 2A, wherein the tissue penetrator has penetrated the skin, muscle, and anterior cortex and entered the intraosseous space;

FIG. 3A is a schematic drawing showing a longitudinal cross-section of an apparatus for accessing sternal bone marrow and a human sternum, wherein the apparatus is positioned on the skin of a human at the location shown in FIG. 1 and the tissue penetrator has penetrated the skin and muscle;

FIG. 3B is a schematic drawing of the apparatus and sternum shown in FIG. 3A, wherein the tissue penetrator has penetrated the skin, muscle, and anterior cortex and entered the intraosseous space;

FIG. 4A is a schematic drawing showing a longitudinal cross-section of an apparatus for accessing sternal bone marrow and a human sternum, wherein the apparatus is positioned on the skin of a human at the location shown in FIG. 1;

FIG. 4B is a schematic drawing of the apparatus and sternum shown in FIG. 4A, wherein the tissue penetrator has penetrated the skin and muscle;

FIG. 4C is a schematic drawing of the apparatus and sternum shown in FIG. 4A, wherein the tissue penetrator has penetrated the skin, muscle, and anterior cortex and entered the intraosseous space;

FIG. 5 is a schematic drawing showing an elevation view of a tissue penetrator having a depth control mechanism actuated by a gear in accordance with the teachings of the present invention;

FIG. 6A is a schematic drawing showing a longitudinal cross-section of an apparatus for accessing sternal bone marrow and a human sternum, wherein the apparatus is positioned on the skin of a human at the location shown in FIG. 1;

FIG. 6B is a schematic drawing of the apparatus and sternum shown in FIG. 6A, wherein the tissue penetrator has penetrated the skin and muscle;

FIG. 6C is a schematic drawing of the apparatus and sternum shown in FIG. 6A, wherein the tissue penetrator has penetrated the skin, muscle, and anterior cortex and entered the intraosseous space;

FIG. 6D is a flowchart of the signal processing between the ultrasound sensing device and driver of FIGS. 6A-6C;

FIG. 7 is a schematic drawing showing a longitudinal cross-section of an apparatus for accessing sternal bone marrow and a human sternum, wherein the apparatus is positioned on the skin of a human at the location shown in FIG. 1, the probe has penetrated the skin and muscle, and the tissue penetrator has penetrated the skin, muscle, and anterior cortex and entered the intraosseous space;

FIG. 8 is a schematic drawing showing a longitudinal cross-section of an apparatus for accessing sternal bone marrow and a human sternum, wherein the apparatus is positioned on the skin of a human at the location shown in FIG. 1, the sliding collar has penetrated the skin and muscle, and the tissue penetrator has penetrated the skin, muscle, and anterior cortex and entered the intraosseous space;

FIG. 9A is a schematic drawing showing a longitudinal cross-section of an apparatus for accessing sternal bone marrow having a vertical reverse clutch mechanism and a human sternum, wherein the apparatus is positioned on the skin of a human at the location shown in FIG. 1;

FIG. 9B is a schematic drawing showing a longitudinal cross-sectional view of the vertical reverse clutch mechanism of the apparatus shown in FIG. 9A with the vertical pin in the engaged position;

FIG. 9C is a schematic drawing showing a longitudinal cross-sectional view of the reverse clutch mechanism of the apparatus shown in FIG. 9A with the vertical pin in the disengaged position;

FIG. 10A is a schematic drawing of a plan view of a horizontal reverse clutch mechanism according to the teachings of the present invention wherein the horizontal pins are in the engaged position, contacting the pawls;

FIG. 10B is a schematic drawing of the horizontal reverse clutch mechanism shown in FIG. 10A, wherein the horizontal pins are in the disengaged position, not contacting the pawls, such that the concentric clutch flywheel comes to a rest;

FIG. 11 is a schematic drawing of horizontal pins with leaf springs, pawls, and the shaft of a horizontal reverse clutch according to the teachings of the present invention;

FIG. 12A is a schematic drawing of an apparatus for accessing sternal bone marrow having a torque or RPM sensor;

FIG. 12B is a schematic drawing of an apparatus for accessing sternal bone marrow having a power sensor;

FIG. 13A is a graph showing the change in torque or amperage as a function of depth of bone penetration with the inflection point marked with an encircled “P” indicating the point at which penetration of the anterior cortex is complete;

FIG. 13B is a graph showing the change in power as a function of depth of bone penetration with the inflection point marked with an encircled “P” indicating the point at which penetration of the anterior cortex is complete;

FIG. 14A is a schematic drawing showing an elevation view of intraosseous tissue penetrators with collars according to the teachings of the present invention;

FIG. 14B is a schematic drawing showing a longitudinal cross-section of an apparatus for accessing sternal bone marrow and a human sternum, wherein the apparatus is positioned on the skin of a human at the location shown in FIG. 1 and the tissue penetrator has penetrated the skin, muscle, and anterior cortex and entered the intraosseous space;

FIG. 15A is a schematic drawing showing a longitudinal cross-section of an intraosseous tissue penetrator assembly with a built-in blade according to the teachings of the present invention and a human sternum, wherein the assembly is positioned on the skin of a human at the location shown in FIG. 1 and the tissue penetrator has not penetrated the skin;

FIG. 15B is a schematic drawing showing a radial cross-section of the tissue penetrator assembly shown in FIG. 15A;

FIG. 15C is a schematic drawing showing a longitudinal cross-section of the tissue penetrator assembly shown in FIG. 15A and a human sternum, wherein the tissue penetrator has penetrated the skin and muscle and the blade has penetrated the skin;

FIG. 15D is a schematic drawing showing a longitudinal cross-section of the tissue penetrator assembly shown in FIG. 15A and a human sternum, wherein the tissue penetrator has penetrated the skin, muscle, and anterior cortex and entered the intraosseous space and wherein the blade is in its retracted position;

FIG. 16A is a schematic drawing showing a longitudinal cross-section of an apparatus for accessing sternal bone marrow according to the teachings of the present invention, wherein the reusable handle and the disposable cartridge are in the disengaged position and the needle shield is attached;

FIG. 16B is a schematic drawing showing a longitudinal cross-section of the apparatus shown in FIG. 16A, wherein the reusable handle and the disposable cartridge are in the engaged position and the needle shield is attached;

FIG. 16C is a schematic drawing showing a longitudinal cross-section of the apparatus shown in FIG. 16A, wherein the reusable handle and the disposable cartridge are in the engaged position, the needle shield is detached, and the needle and probes have been inserted into the soft tissue of a subject;

FIG. 16D is a schematic drawing showing a longitudinal cross-section of the apparatus shown in FIG. 16A and a human sternum, wherein the reusable handle and the disposable cartridge are in the deployed position, the probes have penetrated the skin and muscle, and the tissue penetrator has penetrated the skin, muscle, and anterior cortex and entered the intraosseous space;

FIG. 16E is a schematic drawing showing a longitudinal cross-section of the disposable cartridge shown in FIG. 16D after the handle has been removed;

FIG. 17A is a schematic drawing showing a longitudinal cross-section of an apparatus for accessing sternal bone marrow according to the teachings of the present invention and a human sternum, wherein the reusable handle and the disposable cartridge are in the engaged position, the tissue penetrator has penetrated the skin and muscle;

FIG. 17B is a schematic drawing showing a longitudinal cross-section of the apparatus shown in FIG. 17A, wherein the reusable handle and the disposable cartridge are in the deployed position and the tissue penetrator has penetrated the skin, muscle, and anterior cortex; and

FIG. 17C is a schematic drawing showing a longitudinal cross-section of the disposable cartridge shown in FIG. 17B after the handle has been removed.

DETAILED DESCRIPTION OF THE INVENTION

Some preferred embodiments of the invention and its advantages are best understood by reference to FIGS. 1-17B wherein like numbers refer to same and like parts. Table 1 lists reference numerals with their associated names and figures in which they appear. TABLE 1 No. Feature Name FIGS. 10 housing 2A, 2B, 3A, 3B, 4A, 4B, 4C, 6A, 6B, 6C, 7, 8, 9A, 16A, 16B, 16C, 16D, 17A, 17B 11 cassette 16A, 16B, 16C, 16D, 16E housing 12 flange 2A, 2B, 3A, 3B, 4A, 6A, 6B, 6C, 7, 8, 9A, 16A, 16B, 16C, 16D, 17A 13 support member 16A, 16B, 16C, 16D, 16E 14 end member 16A, 16B, 16C, 16D, 16E 15 cartridge 16A, 16E 16 detent 16A, 16E 17 engaging lock 16A 18 needle shield 16A, 16B 19 reusable handle 16A, 16B, 16C, 16D 20 driver 2A, 2B, 3A, 3B, 4A, 4B, 4C, 6A, 6B, 7, 8 21 battery 2A, 2B, 5, 6A, 6B, 6C, 7, 8, 9A 22 motor 2A, 2B, 5, 6A, 6B, 6C, 7, 8, 9A 23 drive shaft 2A, 2B, 4A, 4B, 4C, 5, 6A, 6B, 6C, 7, 8, 9A, 9B, 9C 24 coupling end 2A, 2B, 6A, 6B, 6C, 7, 8 25 spring 3A, 3B, 16A, 16B, 16C, 16D, 17A, 17B 26 coupling end 3A, 3B 30 tissue 14B, 17B penetrator assembly 31 hub 14B, 17A, 17B, 17C 32 flange 14B, 17A, 17B, 17C 33 screw 14B, 17A, 17B, 17C 34 blade 15A, 15B, 15C, 15D 35 retraction 15A, 15C, 15D lever 40 tissue 2A, 2B, 3A, 3B, 4A, 4B, 4C, 5, penetrator 6A, 6B, 6C, 7, 8, 9A, 9B, 9C, 15A, 15C, 15D, 16A, 16B, 16C, 16D, 16E, 17A, 17B, 17C 41 cannula 14A, 14B, 15B 42 trocar 10A, 10B, 14A, 14B, 15B 43 collar 14A, 15A, 15C, 15D 44 sliding collar 8 45 connector 4A, 4B, 4C, 5, 14B, 16A, 16E, 17A, 17B, 17C 46 central line 10A, 10B, 11, 15B 50 annular stop 2A, 2B, 3A, 3B, 4A, 4B, 4C 51 first 4A, 4B, 4C penetration shoulder 52 threaded 4A, 4B, 4C annulus 53 second 4A, 4B, 4C penetration shoulder 54 third 4A, 4B, 4C penetration shoulder 55 ribs 5 56 gear 5 57 suspension 5 member 58 support annulus 5 60 vertical clutch 9A, 9B, 9C drive member 61 vertical clutch 9A, 9B, 9C flywheel 62 vertical 9A, 9B, 9C engaging pin 63 concentric 10A, 10B clutch drive member 64 concentric 10A, 10B, 11 clutch flywheel 65 horizontal 10A, 10B, 11 engaging pin 66 pawl 10A, 10B, 11 67 coil spring 10A, 10B, 11 68 leaf spring 11 70 probe 7, 16A, 16B, 16C, 16D, 16E 71 ultrasonic 6A, 6B, 6C sensor 90 sternum 1 91 ribs 1 92 skin 2A, 2B, 3A, 3B, 4A, 4B, 4C, 6A, 6B, 6C, 7, 8, 9A, 14B, 15A, 15C, 15D, 16C, 16D, 16E, 17A, 17B, 17C 93 muscle 2A, 2B, 3A, 3B, 4A, 4B, 4C, 6A, 6B, 6C, 7, 8, 9A, 14B, 15A, 15C, 15D, 16C, 16D, 16E, 17A, 17B, 17C 94 bone 2A, 2B, 3A, 3B, 4A, 4B, 4C, 6A, 6B, 6C, 7, 8, 9A, 14B, 15C, 15D, 16D, 17A, 17B 95 anterior cortex 2A, 2B, 3A, 3B, 4A, 4B, 4C, 6A, 6B, 6C, 7, 8, 9A, 14B, 15A, 15C, 15D, 16D, 17A, 17B 96 intraosseous 2A, 2B, 3A, 3B, 4A, 4B, 4C, 6A, space 6B, 6C, 7, 8, 9A, 14B, 15A, 15C, 15D, 16D, 17A, 17B 97 posterior 2A, 2B, 3A, 3B, 4A, 4B, 4C, 6A, cortex 6B, 6C, 7, 8, 9A, 14B, 16D, 17A, 17B

The sternum, as shown in FIG. 1, is a flat, narrow bone comprising three segments, the manubrium, the gladiolus, and the xiphoid process. Each segment includes an intraosseous space bounded by compact bone. According to the present invention, the intraosseous space is the region where cancellous bone and the medullary cavity combine. Bone marrow includes blood, blood forming cells, and connective tissue found in the intraosseous space. For purposes of illustration, compact bone that is nearer to the anterior or dorsal surface shall be referred to as “anterior compact bone” or “anterior bone cortex” and compact bone that is farther from the dorsal or anterior surface shall be referred to as “posterior compact bone” or “posterior bone cortex.”

According to one non-limiting embodiment, an apparatus of the invention may include (a) a driver operable to drive at least a portion of a tissue penetrator into the intraosseous space, (b) a tissue penetrator configured to penetrate the anterior cortex of a sternum, and (c) a depth control mechanism operable to control the depth of penetration of the tissue penetrator into the sternum. For example, in some embodiments, the depth control mechanism may include a pressure-sensing tissue penetrator that transmits pressure changes on insertion to a sensor. The sensor then activates a trigger which in turn activates a motor or other mechanism to cause the tissue penetrator to insert into the intraossesous space a pre-selected depth.

Devices of the invention may be configured in any convenient form. For example, in some embodiments, the tissue penetrator, driver, and depth control mechanism may be arranged in separate housings or bundled in a single housing. Housings of the invention may be formed in any suitable configuration including, without limitation, shapes like a cylinder, a barrel, a bullet, a carpenter's drill, a pistol, or any other convenient form.

Driver

The driver provides power to the tissue penetrator. The power to penetrate the skin, muscle, and anterior cortex may be supplied to the tissue penetrator by any suitable means including, without limitation, one or more of the following: a battery, a spring, compressed gas, manual force, and any other mechanical or electrical source of rotation or reciprocation. The power may also be supplied directly or indirectly (e.g. using gears) by the operator and/or the patient. In addition to batteries, electric power may come from any other suitable source including conventional hospital or home wall outlets. The power source may be operably coupled with a motor. Motors of the invention may be selected from the group consisting of DC motors, AC motors, compressed gas motors, wound spring motors, and reciprocating motors. Motors of the invention may also be coupled to one or more gears, which may optionally be positioned in one or more gear boxes.

According to the embodiment of the invention shown in FIGS. 2A and 2B, driver 20 includes battery 21 and motor 22 that are electrically coupled and contained within housing 10. Driver 20 also includes drive shaft 23 operably linked to motor 22. Driver 20 further includes coupling end 24 attached to drive shaft 23. Coupling end 24 in this and other embodiments may include a gear box. Similarly, FIGS. 6A, 6B, 6C, 7, 8, 9A, and 14B show other embodiments in which the driver may include like batteries, motors, and drive shafts.

According to the embodiment of the invention shown in FIGS. 3A and 3B, driver 20 includes spring 25 and coupling end 26 wherein spring 25 and coupling end 26 are connected and contained within housing 10. By contrast, according to the embodiment shown in FIGS. 16A, 16B, 16C, 16D, 17A, and 17B, driver 20 includes spring 25 without a connecting member. Spring 25 may be directly or indirectly coupled to the closed-end of the housing fixing the position of that end of spring 25. In some embodiments of the invention, coupling end 26 may further include a trigger mechanism for releasably holding spring 25 in a compressed “ready” position, a sensor for detecting pressure changes from the tissue penetrator and any other necessary relay circuit required to activate the trigger and or driver.

Tissue Penetrator

Typically, a tissue penetrator will include an outer sheath, such as a needle and an inner trocar. Tissue penetrators of the invention may include in various combinations a needle, a needle set, a cannula, a trocar, a stylet, a catheter, or combinations thereof. Needles that are suitable for use in the present invention may be from about twenty gauge to about ten gauge. In some preferred embodiments, a tissue penetrator includes an outer needle or cannula and an inner trocar or stylet. In these embodiments, the trocar or stylet may prevent clogging of the needle by bone fragments during the drilling process. The tissue penetrator may include a needle set in which the component trocar and cannula are ground together to produce a matched set of a specific design to facilitate passage through bone.

According to the invention, a tissue penetrator assembly includes a tissue penetrator. It may further include a collar, a connector, a hub, and combinations thereof. Collars of the invention, when present, may serve as depth control mechanisms. Connectors or hubs may serve as a means to connect an inserted catheter to a source of fluids or drugs including without limitation, blood, intravenous fluids of various formulations and any other fluid or medication suitable for intravenous administration.

In some embodiments, a connector or hub may be any structure that supports or permits unidirectional or bidirectional access to the intraosseous space. Connectors may include one or more locking mechanisms to prevent accidental disconnections between a source of intravenous fluid and the inserted cannula. Connectors such as Luer locks may be male or female. In some preferred embodiments, a connector is a luer lock.

According to the present invention, a tissue penetrator assembly may further include a hub with a flange to protect the skin and to stabilize the device after insertion into a human's sternum. The hub also provides a handle to remove the IO needle after use. The hub flange is the flat end of the hub that is nearer to the skin. Hubs may be made of any material, preferably a material that may be rendered sterile.

In one specific embodiment, shown in FIG. 14B, tissue penetrator assembly 30 includes connector 45, hub 31 with flange 32, screw 33, cannula 41 and collar 43. As shown, the stylet has been removed.

In some embodiments of the invention, the tissue penetrator may be propelled into the IO space without rotation. This may be by direct manual force, or by a reciprocating action. In some embodiments, the needle may be rotated about its longitudinal axis in order to facilitate entry into the IO space. The needle may be rotated even where a driver including a spring is used. One way to rotate a spring-driven needle is to rotatably couple it with the housing. For example, a spring-driven needle may be fixedly attached to a coupling end having male threads on its outer circumference. This coupling end may be mated with a housing with corresponding female threads on its inner circumference. Consequently, as the spring propels the coupling end and attached needle through the housing, the coupling end would rotate. A spring may also be used to drive a tissue penetrator into the IO space by an impact force without rotation.

As a further aid to IO entry, a small incision may be made in the patient's skin at the site where IO entry is desired. For example, if a collar is included with the apparatus, a skin incision will facilitate passage of the tissue penetrator to the bone. The incision may be formed using any suitable surgical blade, which may optionally form part of the tissue penetrator assembly. One or more blades may be included. Blades may be configured to be collapsible, removable, or retractable.

For example, according to the embodiment shown in FIG. 15B, retractable blade 34 is movably attached to opposite sides of cannula 41 in a plane parallel to the longitudinal axis of cannula 41. As shown in FIG. 15C, blade 34 may be used in a simple process to automatically form an incision in skin 92 at the proper place and of the proper size to permit ingress of tissue penetrator 40, which includes cannula 41 and trocar 42, and collar 43. The initial incision may be made by the needle itself as shown in FIG. 15A. The opposing blade configuration allows blade 34 to retract so that the drilling process may proceed after insertion. Retraction may be accomplished by actuating retraction lever 35 (FIG. 15D). Although not expressly shown, the opposing blade configuration may also allow the use of break-away blades that are removed after insertion, but prior to drilling.

Depth Control Mechanism

According to the teachings of the present invention, sternal IO access devices may incorporate a mechanism to prevent over-penetrating the sternum, which could potentially damage underlying structures in the chest cavity. This mechanism may include mechanical stops, electrical stops, depth detectors, and combinations thereof. An electrical stop may prevent the operator from over-drilling by interrupting drill rotation and/or advancement when it detects that the needle tip has penetrated into the sternal IO space. An electrical stop may include a pressure-sensing tissue penetrator connected to a sensor that activates a trigger to control the driver such that a tissue penetrator is inserted to a pre-selected depth in the IO space. An electrical stop may also accurately detect the location of the cortex so that the tissue penetrator may be safely advanced to a predetermined depth in the IO space. An electrical stop may include a torque detector, an ultrasound probe, a mechanical probe, or a fluid detector.

Mechanical stops include a preset drill depth (similar to a stop on a commercial drill), a collar attached to a needle or tissue penetrator, and a reverse clutch mechanism that prevents further drilling once the needle tip enters the intraosseous space of the sternum. Mechanical stops may have a fixed position or may be adjustable. If the mechanical stops are adjustable, they may be preset or adjusted while drilling is in progress. As shown in FIG. 2, annular stop 50 is a rib that traces the inner circumference of housing 10 and arrests advancement of tissue penetrator 40 by physically obstructing passage of coupling end 24. In the embodiment shown in FIG. 3, annular stop 50 obstructs passage of coupling end 26. Such physical stops may also be formed in any other suitable shape including, without limitation, arcs, bars, bumps, and ridges. Other options include a track including a groove of finite length on the inner surface of the housing and a corresponding ridge on the outer circumference of the coupling end.

The embodiment shown in FIGS. 14A and 14B illustrates that the depth of needle penetration may also be controlled by forming an enlargement or ridge around (e.g. collar) the tissue penetrator. Collar 43 is preset at the desired distance from the needle tip to assure proper placement of the device. Collar 43 may be cylindrical with symmetrically beveled ends to promote easier entry through the skin as shown in the left side of FIG. 14A or any other suitable shape and configuration necessary to achieve its purpose. Alternatively, collar 43 may have a beveled proximal end and a sheer distal end as shown in the right side of FIG. 14A. The acute angle or right angle of the distal end of collar 43 may promote a more secure stop against accidental over-penetration. The proximal end of collar 43 remains tapered to promote easy egress from the skin.

Another non-limiting embodiment of a mechanical stop is a gear that engages ridges on the drive shaft (FIG. 5) thus allowing depth control without interfering with rotation of tissue penetrator 40. Gear 56 is rotatably coupled to suspension member 57, which in turn is mounted on support 57. As shown in FIG. 5, gear 56 is disengaged from ribs 55. While not expressly pictured, gear 56 may contact and engage ribs 55 by any suitable mechanism. A gear of the invention may be configured to rotate a preset number of revolutions. Alternatively, the gear may be spring-loaded such that resistance increases with advancement, thereby creating a counter-balancing force to the driver. Devices with such gears may further reduce the possibility of penetrating or damaging the posterior cortex and underlying organs. A gear may also be operably linked to a sensor such that it may engage the drive shaft ribs 55 and stop needle advancement upon satisfaction of a pre-selected threshold.

The invention also provides embodiments in which a reverse clutch mechanism is used to arrest bone penetration (FIGS. 9-11). According to the embodiment of the invention shown in FIG. 9A, drive shaft 23, which is rotatably coupled with motor 21, is fixedly connected to vertical clutch drive member 60. Vertical clutch drive member 60 is releasably coupled to vertical clutch flywheel 61 by vertically engaging pin 62 (FIGS. 9A and 9B). Flywheel 61 is fixedly connected with tissue penetrator 40 such that withdrawal of vertically engaging pin 62 (FIG. 9C) interrupts the transfer of force from motor 21 to tissue penetrator 40. Accordingly, tissue penetrator 40 may come to rest due to incidental frictional forces or an active breaking mechanism.

As pictured, vertical engaging pin is spring loaded. Pin 62 may be configured to remain engaged only so long as lateral forces (torque) during the drilling process are maintained above a certain level. One may select or adjust the threshold torque required to maintain engagement, by selecting springs with a particular spring constant. As soon as the torque falls below this threshold, as it would when the needle penetrates the anterior cortex and enters the IO space, pin 62 withdraws, disengaging the driver.

The reverse clutch mechanism may also be configured as concentric rings, one embodiment of which is illustrated in FIG. 10. In these embodiments, the drive shaft may be fixedly attached to a concentric clutch drive member. Concentric clutch drive member 63 is releasably coupled to a concentric clutch flywheel 64 by horizontal engaging pins 65 and pawls 66. FIG. 10A shows an embodiment of the invention in which horizontal engaging pins 65 are engaged and concentric clutch drive member 63 rotates flywheel 64. Horizontal engaging pins 65 each include coil spring 67. When the tip of the tissue penetrator 40 has entered the IO space, horizontal engaging pins 65 withdraw from pawls 66 such that concentric clutch drive member 63 can no longer rotate flywheel 64 (FIG. 10B). Flywheel 64 and its associated tissue penetrator may then come to rest due to incidental frictional forces or an active breaking mechanism. According to some non-limiting embodiments of the invention, horizontal engaging pin 65 may further include a leaf spring 68 that releasably engages pawl 66 (FIG. 11). Both coil spring 67 and leaf spring 68 may be configured to be torque sensors.

Depth control mechanisms of the invention may include one or more depth sensors or probes. In one embodiment, depth sensors or probes may include pressure sensors. An example of this embodiment is shown in FIG. 7, wherein probes 70 are operably linked to coupling end 24, which may contain a pressure sensor and a trigger. Pressure on the tips of probes 70 upon contacting bone is relayed to the sensor which activates the trigger. The trigger then starts advancement of tissue penetrator 40 by activating the driver (FIG. 7). Tissue penetrator 40 may be advanced a preset distance calculated to place the tip of tissue penetrator 40 in the intraosseous space. Rotational forces (drilling), as opposed to impact forces, may be less traumatic on the bone and more precise in its application.

FIG. 8 illustrates another non-limiting embodiment of a closely-fitting, cylindrical collar 44, which encloses tissue penetrator 40, that may be used to locate anterior cortex 95. Collar 44, according to this embodiment, slides relative to tissue penetrator 40 along the longitudinal axis of tissue penetrator 40. In its starting position, tissue penetrator 40 is recessed within collar 44. As shown in FIG. 8, upon making contact with anterior cortex 95, sliding collar 43 slides up into coupling end 24, which activates motor 22 to drill a predetermined distance into the bone. Motor 22 may be rotational or reciprocating. More generally, sliding collar 43 may be used to activate a driver of any kind.

Depth control using an IO device of the present invention may proceed in two stages as shown in FIG. 4. In the first stage, the needle may be advanced through the relatively soft tissues of the skin, subcutaneous tissue and muscle. In the second stage, the needle is drilled or driven through the much harder anterior cortex.

According to the embodiment of the invention shown in FIG. 4A, the device includes housing 10, battery 21, motor 22, drive shaft 23, tissue penetrator 40, connector 45, annular stop 50, first penetration shoulder 51, threaded annulus 52, second penetration shoulder 53, and third penetration shoulder 54. The tissue penetrator assembly, according to this embodiment, includes tissue penetrator 40, connector 45, first penetration shoulder 51, threaded annulus 52, second penetration shoulder 53, and third penetration shoulder 54. The drive shaft may or may not rotate tissue penetrator 40 as it advances. Each annulus may include a pressure sensor, a trigger, or both a pressure sensor and a trigger. First penetration shoulder 51 is fixedly connected to threaded annulus 52 and drive shaft 23. Second penetration shoulder 53 is rotatably mounted on threaded annulus 52. Third penetration shoulder is slidably mounted on tissue penetrator 40. As shown, the device is in its “ready” or undeployed position.

The first stage of insertion is initiated when an operator contacts the device with the skin. Other activation methods are also possible. Upon contacting skin 92 and applying pressure, a first sensor activates advancement of the tissue penetrator assembly. As the tissue penetrator advances, third penetration shoulder 54 is stopped by annular stop 50. The rest of the tissue penetrator assembly continues to advance such that second penetration shoulder 53 contacts third penetration shoulder 54 (FIG. 4B). Concurrently, the tip of tissue penetrator 40 contacts anterior cortex 95 as shown in FIG. 4B.

This contact together with continued application of pressure by the operator initiates the second stage by triggering a second sensor to activate motor 22. Motor 22 then propels first penetration shoulder 51 the preset or operator-set distance to second penetration shoulder 53. This, in turn, advances the tip of tissue penetrator 40 through anterior cortex 95 and into IO space 96 as shown in FIG. 4C.

Depth Probes or Sensors

Devices of the present invention may include various depth probes or sensors that detect the location of the needle, the bone, or both. Sensors are preferably connected to a control mechanism (e.g. a logic board) that determines whether needle advancement shall begin, continue, or terminate. Control mechanisms may also be mechanical or triggers. Sensor detection and controller evaluation may be intermittent, periodic or continuous.

For example, an ultrasonic detector may be used to locate the sternal cortex. In the non-limiting embodiment, shown in FIG. 6A, tissue penetrator 40 is in the storage or undeployed position. Ultrasonic sensor 71 detects the distance between the device (e.g. flange 12) and IO space 96. Ultrasonic sensor 71 may also detect the position of tissue penetrator 40. FIG. 6B shows tissue penetrator 40 in contact with anterior cortex 95, ready for penetration. Detection by ultrasonic sensor 71 allows the device to tailor further advancement of the cannula to the exact dimensions of the targeted bone (FIG. 6C). This may be particularly advantageous given the variability from patient to patient and variations due to compression of skin and muscle by the device operator. This signaling process is outlined in the flowchart shown in FIG. 6D. Briefly, a sensor detects tissue penetrator, bone location, or both. This data is communicated to a logic board that measures or calculates the distance from the sensor to the bone. Upon obtaining this information, the driver is activated to advance the tissue penetrator the appropriate distance to achieve bone penetration.

Bone cortex is very dense requiring considerable force to penetrate. As soon as the needle or drill passes through the cortex and enters the intraosseous space a pronounced change is noted in the force required to advance the needle. Resulting changes may be a decrease in torque and an increase in motor revolutions per minute (RPM). These changes can be measured and used to switch off the motor or activate a brake to prevent additional, potentially dangerous drilling activity.

Thus, sensors of the invention may detect torque, revolutions per minute (RPM), backpressure, power consumption or any other relevant measure of needle advancement. In the embodiment shown in FIG. 12A, the sensor is mechanically coupled to the motor and detects torque and/or RPMs and activates the switch. Thus, the sensor may be a shaft encoder. By contrast, the embodiment shown in FIG. 12B the sensor is coupled to the electrical circuit between the motor and the power source and detects amperage and/or voltage.

FIG. 13A illustrates the changes in torque or amperage as a function of drilling time or depth of penetration. At the time of penetration (P), the sensor may detect the decrease in torque or amperage and may discontinues needle advancement. If the needle is rotating, a brake may be applied to bring it to rest.

FIG. 13B illustrates the changes in RPM or voltage as a function of drilling time or depth of penetration. At the time of penetration (P), the sensor may detect the decrease in torque or amperage and may discontinues needle advancement. If the needle is rotating, a brake may be applied to bring it to rest.

Probes and sensors of the invention may be operably coupled to a driver, a tissue penetrator, a depth control mechanism, or portions or combinations thereof. In one non-limiting embodiment, the tissue penetrator itself may be or include a depth probe or sensor.

Reusable Handle/Disposable Cartridge

The present invention provides intraosseous access devices with a reusable handle and a disposable cartridge containing the needle, one embodiment of which is illustrated in FIG. 16. The advantage of these devices over currently available devices is the overall size and weight reduction of carrying multiple devices in the field, such as in the medical pack by army medics. Ten (10) units of currently disposable IO devices weigh far more and take much more space than one reusable handle with 10 disposable needle assemblies. The greater part of the weight and size may be in the reusable handle. Reusable handles may contain a driver in accordance with the teachings of the present invention. Disposable cartridges may include tissue penetrator assemblies and depth sensors in accordance with the teachings of the present invention. Disposable cartridges of the invention may engage or lock into the reusable handle with a recess and detent or any other mechanism.

FIG. 16A illustrates an embodiment of an IO device of the invention including reusable handle 19 and disposable cartridge 15. This figure shows the handle separate from cartridge 15 as seen prior to connecting for use. Cartridge 15 includes tissue penetrator 40, probes 70, detent 16, coupling member 13, and end member 14. Cartridge 15 further includes releasable needle shield 18. Tissue penetrator 40 and probes 70 are covered by needle shield 18 to protect the user from accidental needle sticks and preserve tissue penetrator 40. Shield 15 may have a domed surface as shown or a flat surface to allow the cartridge to stand alone. While not shown in the figure, cartridges of the invention may further include, without limitation, hubs, flanges, screws, and bolts.

Reusable handle 19 includes housing 10, spring 25, and engaging lock 17. Engaging lock 17 engages detent 16 upon insertion of cartridge 15 into handle 19. As a result, cartridge 15 may “pop” or snap into reusable handle 19 (FIG. 16B). Although not expressly pictured, cartridge 15 and handle 19 may include a locking mechanism that is engaged by twisting cartridge 15 into handle 19. Needle shield 18 may be removed when ready for use (FIG. 16C). Deployment of tissue penetrator 40 is similar to that described for other embodiments. See e.g. FIG. 8. Briefly, compressed spring 25 is released upon probes 70 contacting anterior cortex 95. As spring 25 expands, it propels tissue penetrator 40 through anterior cortex 95 and into intraosseous space 96 (FIG. 16D). Thereafter, reusable handle 19 may be removed and a access to intraosseous space 96 may be gained through connector 44 (FIG. 16E). Spring 25 need not contact connector 45, but may contact a plate or other struction (not expressly shown) that drives tissue penetrator 40 into bone 94.

As shown in FIG. 17A, a driver (here spring 25) in accordance with the invention is shown in the undeployed, ready position. Contact with skin 92 may activate the spring 25, which causes tissue penetrator 40 to penetrate skin 92, muscle 93, and proximal cortex 95. Advancement of tissue penetrator 40 continues until collar 42 contacts proximal cortex 95 (FIG. 17B). Thus, according to this embodiment, flange 32 acts as the depth control mechanism. Other depth control mechanisms may also be employed such as a probe, sensor, rib and any combination thereof. Once advancement is arrested, the end of tissue penetrator 40 is positioned in intraosseous space 96.

The reusable handle, which here includes housing 10 and spring 25, may be removed leaving tissue penetrator assembly 30 behind (FIG. 17C). Tissue penetrator assembly 30 includes hub 31 to provide stabilization of tissue penetrator 40 against the skin and to provide for additional security against accidental advancement or dislodgement during patient transport. Hub 31 incorporates a flange 32 at its distal end to provide for skin safety and better stabilization. After insertion of tissue penetrator 40 into the IO space hub 31 is adjusted by screw 33 or other mechanism so that it snuggly fits against the skin. Tissue penetrator 40 may be fixedly attached to screw 33 either before insertion or after insertion (e.g. by a locking mechanism). IO space 96 may then be aseptically accessed through connector 45.

Methods

One aspect of the invention is a method of establishing access to the intraosseous space including contacting the skin covering the manubrium of a subject with a device including a driver, a tissue penetrator, and a depth control mechanism, deploying the tissue penetrator. The term “subject” may include any vertebrate with a sternum. The term “operator” may include anyone who uses a device of the invention including, without limitation, a health care professional and the subject. The term “deploying the tissue penetrator” may mean advancing the tissue penetrator from its starting position a sufficient distance to situate the tip of the tissue penetrator in the IO space. The method may further include detaching the driver from the tissue penetrator after insertion of the tissue penetrator is achieved.

For example, according to the embodiments pictured in FIGS. 2-3, the operator inserts tissue penetrator 40 into the subject at the region shown in FIG. 1. Tissue penetrator 40, which includes a pressure sensor, detects the increase in pressure that occurs when the tip contacts anterior cortex 95. The sensor then activates driver 20 to advance tissue penetrator 40 until coupling end 24 (FIG. 2) or coupling end 26 (FIG. 3) contacts annular stop 50. While not expressly shown, a connector recessed in the coupling end may be used to access IO space 96. This access may optionally involve removal of portions of the device, such as housing 10, driver 20, driver shaft 23, and coupling end 24 or 26.

In a related embodiment shown in FIG. 5, tissue penetrator 40 includes a pressure-sensor (not expressly shown). Upon application of an axial force by the operator against the subject's sternum, tissue penetrator pierces the subjects skin, muscle, and subcutaneous tissue to contact bone. The sensor either directly or indirectly activates motor 22 to rotate tissue penetrator 40, thereby beginning drilling into the bone. Simultaneously or subsequently, gear 56 may engage ribs 55 to regulate the depth of drilling. For example, upon detecting a drop in pressure, the sensor may directly or indirectly brake or block further rotation of gear 56.

Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alternations can be made herein without departing from the spirit and scope of the invention as defined by the following claims. 

1. An apparatus for accessing the bone marrow inside a bone comprising: a tissue penetrator; a driver operable to drive a portion of the tissue penetrator into the bone marrow; a trigger mechanism configured to engage when a portion of the tissue penetrator contacts a bone; and a depth control mechanism operable to control the depth of penetration of the tissue penetrator.
 2. The apparatus of claim 1 wherein the driver comprises a motor.
 3. The apparatus of claim 1 wherein the driver further comprises a power source selected from the group consisting of a battery, a coiled spring, a compressed gas, and a solar power cell.
 4. The apparatus of claim 1 wherein the depth control mechanism comprises a collar wherein the collar surrounds the tissue penetrator.
 5. The apparatus of claim 1 wherein the depth control mechanism comprises a probe.
 6. The apparatus of claim 1 wherein the depth control mechanism comprises an ultrasonic sensor.
 7. The apparatus of claim 1 wherein the trigger mechanism comprises a gear operable to control the depth of penetration of the tissue penetrator.
 8. The apparatus of claim 1 wherein at least one longitudinal probe extends from the trigger mechanism to the bone, the probe operable to contact the bone and activate the trigger mechanism.
 9. The apparatus of claim 1 wherein the trigger mechanism includes a spring-loaded reverse clutch mechanism operable to disengage the tissue penetrator from the motor at a preset torque level or a preset revolutions per minute level.
 10. The apparatus of claim 1 wherein the depth control mechanism comprises a pressure-sensing tissue penetrator operable to transmit pressure changes to the trigger mechanism.
 11. The apparatus of claim 1 wherein the trigger mechanism is operable to activate the driver to drill to a pre-selected depth.
 12. The apparatus of claim 1 wherein the bone is the sternum.
 13. An apparatus for accessing the bone marrow comprising: a tissue penetrator operable to detect changes in pressure; a driver operable to drive a portion of the tissue penetrator into the bone marrow; a trigger mechanism operable to activate the driver; a sensor operable to receive signals from the tissue penetrator and transmit them to the trigger mechanism.
 14. The apparatus of claim 13 wherein the trigger mechanism is operable to activate the driver to drill to a pre-selected depth.
 15. The apparatus of claim 13 wherein the sensor is a pressure sensor.
 16. The apparatus of claim 13 wherein the driver is selected from the group consisting of manual force, a motor, a coiled spring, and a compressed gas cartridge.
 17. The apparatus of claim 13 wherein the bone is the sternum.
 18. An apparatus for accessing the bone marrow inside a bone comprising: a tissue penetrator configured to penetrate the bone marrow, the tissue penetrator comprising an outer cannula and an inner trocar; a driver operable to drive the tissue penetrator into the bone marrow; a flange operable to stabilize the tissue penetrator after the cannula is inserted into the bone marrow, the flange moveable along the longitudinal axis of the tissue penetrator; and a circumferential collar configured to limit the depth of penetration of the tissue penetrator into the bone marrow.
 19. The apparatus of claim 18 wherein the apparatus comprises a luer lock connector.
 20. The apparatus of claim 18 wherein the tissue penetrator comprises a blade.
 21. An apparatus for accessing the bone marrow inside a bone comprising: a reusable handle configured to engage a disposable cartridge; a cartridge comprising: a tissue penetrator configured to penetrate the bone marrow, the tissue penetrator comprising an outer cannula and an inner trocar; a depth control mechanism; and a driver operable to drive the tissue penetrator into the bone marrow.
 22. The apparatus of claim 21 wherein the depth control mechanism comprises a mechanical probe.
 23. The apparatus of claim 21 wherein the driver comprises a power source selected from the group consisting of a battery, a coiled spring, a compressed gas, and a solar power cell.
 24. An apparatus for accessing the bone marrow inside a bone comprising: a cartridge configured to penetrate the bone, a tissue penetrator; the depth control mechanism; and a flange operable to stabilize the tissue penetrator at a desirable level in the bone, the flange moveable along the vertical axis of the tissue penetrator; and a reusable handle configured to engage a tissue penetrator cartridge comprising a driver operable to drive the tissue penetrator into the bone marrow.
 25. An apparatus for penetrating a bone comprising: a housing; a tissue penetrator assembly, comprising a trigger mechanism configured to engage when the tissue penetrator contacts the bone and a mechanism operable to control the depth of penetration of the tissue penetrator into the bone; a coupling end operable to releasably attach the penetrator assembly to a drive shaft; a drive shaft operable to connect the penetrator assembly to a gear assembly; a gear assembly operable to engage and rotate the drive shaft; a motor operable to engage the gear assembly and drive the penetrator into the bone marrow; and a driver operable to power the motor.
 26. An apparatus for accessing the bone marrow inside a bone comprising: a tissue penetrator configured to penetrate the bone; and a sensor mechanism configured to detect depth of tissue penetrator penetration into the bone marrow.
 27. An apparatus for accessing the bone marrow inside a bone comprising: a handle; and a cartridge configured to attach to the handle, the cartridge comprising a tissue penetrator, and a depth control mechanism.
 28. An apparatus for accessing the bone marrow inside a bone comprising: a handle comprising a coiled spring; and a cartridge configured to insert into the handle, the cartridge comprising a tissue penetrator and a flange operable to contact a human's tissue.
 29. The apparatus of claim 28, the tissue penetrator comprising: a connector; a screw; a flange operable to move along the screw; a cannula; and a trocar.
 30. The apparatus of claim 28 wherein the bone is the sternum.
 31. An apparatus for accessing the bone marrow inside a bone comprising: a tissue penetrator configured to the bone marrow, the tissue penetrator comprising an outer cannula and an inner trocar; a driver operable to drive the tissue penetrator into the bone marrow; and a flange operable to stabilize the tissue penetrator after the cannula is inserted into the bone marrow, the flange moveable along the longitudinal axis of the tissue penetrator.
 32. An apparatus for accessing the bone marrow inside a bone comprising: a driver; a trigger operably linked to the driver; and a tissue penetrator having a depth sensor operably linked to the trigger.
 33. A method for accessing the intraossesous space of a bone comprising: contacting the skin covering the bone with a device having: a tissue penetrator configured to penetrate the intraossesous space, the tissue penetrator comprising an outer cannula and an inner trocar; a driver operable to drive a portion of the tissue penetrator into the intraosseous space; and a depth control mechanism operable to control the depth of penetration of the tissue penetrator into the intraosseous space; advancing the tissue penetrator a sufficient distance to place at least a portion of the cannula in the intraossesous space; and removing the trocar from the cannula.
 34. The method of claim 33 wherein the bone is the sternum.
 35. A method for manufacturing an apparatus for accessing the bone marrow inside a bone comprising: forming a tissue penetrator configured to penetrate a bone and provide access to the bone marrow, the tissue penetrator comprising an outer cannula and an inner trocar; a driver operable to drive a portion of the tissue penetrator into the bone marrow; and a depth control mechanism operable to control the depth of penetration of the tissue penetrator into the bone. 